1. Field of the Invention
A gravity flow display device for exhibiting two related displays such that one display is visible while the other is blocked from view and vice versa.
2. Description of the Prior Art
Devices to display photographs and other items are known in the art. Two or more such items which are related to one another are often displayed in a frame with multiple display portions, however in this type of display arrangement all of the related items are concomitantly visible to a viewer.
Also known in the art are timers consisting of two transparent hourglass compartments connected by a constricted passageway. The timers contain therein sand or other non-transparent particulate matter which can alternatingly flow from one hourglass compartment to the other in response to gravitational force.
British Pat. No. 712,805 discloses two hourglass compartments connected by a constricted passageway, one of said two compartments being substantially full of sand. The two hourglass compartments form a part of a parking meter. Each compartment contains therein a sign reading "violation," said sign being blocked when the compartment it is within is in its lower filled position or when in its upper position with enough sand in it. The hourglass parking meter contains a substantial amount of sand and hence it takes a significant period of time for a lower position compartment to fill up and render the sign therein non-visible.
Other relevant patents are U.S. Pat. Nos. 679,701; 1,002,227; 1,627,270; 3,438,197; 3,692,382.